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Material Science
XGT
XGT13
Micro-XRF analysis for metal debris and particle analysis
The characterisation of microscopic particles remains an important task for analysts, whether in forensic
science (eg, glass fragments, paint flakes, gun shot residues), environmental science (eg, soil, atmospheric
pollutants, cosmic dust), geology (eg, rock particles for mining exploration) and engineering (engine wear
debris).
The bench top XGT-5000 x-ray fluorescence (XRF) micro-analyser is ideally suited for just such analysis, for
it offers fast, non-destructive elemental characterisation with a unique high spatial resolution (10 µm). The
analysis is both qualitative and quantitative, so it can quickly identify specific elements present or provide
compositional information with ppm/percent accuracy (eg, specific alloy chemistry)
Metal paticle analysis
Analysis of engine wear debris is an important example
where micro-XRF is particularly well suited. Jet engines
in regular use experience continuous wear on the various
parts of the engine (eg, gearbox, bearings) which results in
small metal fragments entering the lubrication oil channels.
These can be collected using carefully placed magnets,
and are then analysed. Since different metals and alloys are
used in the different engine components, by characterising
the metallic composition of the fragments it is possible to
identify the origin of the wear particles. This provides an
engineering team with valuable information concerning the
overall engine health.
Similar analyses are used in troubleshooting roles in many
manufacturing plants, as a method of providing very fast,
detailed composition analysis of small metal fragments.
Making the analysis
The XGT-5000 offers high intensity x-ray beams with 100
µm and 10 µm diameters, thus allowing a wide range of
particle sizes to be efficiently analysed. The particles can be
simply deposited on the sample stage, or affixed to double
sided tape (which is elementally clean for XRF purposes).
Low and high magnification cameras provide clear images
of the particles, and it is a simple matter to locate a specific
particle for analysis (see Figure 1).
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Figure 3: High resolution optical image of metal fragments. The red circle indicates the 100 µm analysis spot.
Alternatively, it is possible to scan an area automatically, to
build up a detailed elemental image, covering a very large
number of particles in one analysis. Thus it is possible
to very quickly locate specific particles of interest, which
can then be reanalysed in detail if necessary. Once the
data has been acquired, a spectral searching module can
be used to compare the spectrum with previously saved
spectra (from known components), to provide fast and
simple identification.
Results
In this example, metal particles trapped in a filter were
transferred to a thin polymer sheet and analysed with the
XGT-5000.
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excellent beam properties possible with the unique 10 µm
x-ray beam on the XGT-5000 allow the shapes of the individual particles to be very accurately imaged. This can provide further indications on the origin of a particle, and the
manner in which it was formed.
Figure 2: Optical image (left) and element image (right) of microscopic metal particles
Figure 2 illustrates the low resolution optical image taken
over a 10 cm x 10 cm area, with hundreds of particles
visible, ranging from a few mm, down to a few 10 s of microns in size. A composite element image is also shown,
illustrating the majority of the particles to be mainly composed of iron, whilst a smaller of number of copper and/or
aluminium fragments are also present. Four particles were
chosen for more detailed analysis (labelled in green).
Figure 4: Optical and element images acquired over small area of particles with
10 µm beam diameter. The mapping area relative to the original large area scan is
marked by the yellow box in the top left image.
Summary
Fast analysis of minute particles is an important requirement in many varied applications. As illustrated here, the
XGT-5000 micro-XRF system is ideally suited for such work,
with x-ray beams of 10 µm and 100 µm diameters allowing
discrete analysis of the particles. In addition, the automated
XY scanning function enables large numbers of particles to
be imaged, allowing the easy location of areas of interest.
The quantitative nature of XRF provides specifical compositional characterisation of different metals/alloys.
Figure 3: XRF spectra acquired from particles indicated in Figure 2.
Finally, in order to demonstrate the high resolution imaging capability of the XGT-5000, a small area of the original sample was chosen for analysis with the 10 µm beam.
Although many of the particles are relatively large (50-100
µm), smaller fragments are also apparent (<30 µm). The
XGT-5000
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Spot analyses on these representative particles are shown
in Figure 3. Particles 1 and 3 are dominated by aluminium,
and quantitative analysis indicates these are high purity
aluminium (>99%) and aluminium-copper alloy (including
other low concentration metals such as lead). Particle 2 is
a steel, with >99.9% iron and trace amounts of chromium
and manganese. Particle 4 is identified as a tin bronze (copper-lead-tin alloy) – the spectrum is dominated by copper
(>80%) but with significant lead and tin content too.